Yet another thump problem. ;-)
 

In article , Don Pearce
wrote:

Mosfets are an excellent alternative to relays these days. On resistance
of a few milliohms in cheap packages.

And should work OK with something like a 405 that has current limiters.

However I must confess that the impression I've gained is that here the
problem may be being injected into the input of the 405. If so, using small
signal devices to clamp that to ground might be cheaper and more effective.

Jim

--
Please use the address on the audiomisc page if you wish to email me.
Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm
Armstrong Audio http://www.audiomisc.co.uk/Armstrong/armstrong.html
Audio Misc http://www.audiomisc.co.uk/index.html

Yet another thump problem. ;-)
 

Don Pearce wrote:



** The non sealed types I have come across develop bad contacts
( high resistance) and cleaning them is PITA.



Mosfets are an excellent alternative to relays these days. On
resistance of a few milliohms in cheap packages.


** Shame about the many drawbacks, like having an *internal diode* in parallel and needing to be driven with a gate voltage to get that low resistance.

Not a practical alternative to a DPDT mini-relay you can by for a couple of dollars.

http://sound.westhost.com/articles/muting.html#s4


..... Phil

Yet another thump problem. ;-)
 

On Thu, 2 Jun 2016 05:14:05 -0700 (PDT), Phil Allison
wrote:

Don Pearce wrote:



** The non sealed types I have come across develop bad contacts
( high resistance) and cleaning them is PITA.



Mosfets are an excellent alternative to relays these days. On
resistance of a few milliohms in cheap packages.


** Shame about the many drawbacks, like having an *internal diode* in parallel and needing to be driven with a gate voltage to get that low resistance.

Not a practical alternative to a DPDT mini-relay you can by for a couple of dollars.

http://sound.westhost.com/articles/muting.html#s4


.... Phil



Just use enhancement mode devices. Gate up at source voltage - the FET
is off. Drag it down by five volts, it is fully on. Pretty much the
same driving method as a five volt relay. And no contacts to get
dirty.

d

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Yet another thump problem. ;-)
 

Don Pearce wrote:

Phil Allison

Don Pearce wrote:



** The non sealed types I have come across develop bad contacts
( high resistance) and cleaning them is PITA.



Mosfets are an excellent alternative to relays these days. On
resistance of a few milliohms in cheap packages.


** Shame about the many drawbacks, like having an *internal diode*
in parallel and needing to be driven with a gate voltage to get that
low resistance.

Not a practical alternative to a DPDT mini-relay you can by for a
couple of dollars.

http://sound.westhost.com/articles/muting.html#s4




Just use enhancement mode devices. Gate up at source voltage - the FET
is off. Drag it down by five volts, it is fully on. Pretty much the
same driving method as a five volt relay. And no contacts to get
dirty.


** Same bull**** as before, one mosfet will not do the job for line level signals and having to bias it on makes it almost useless.

The link I quoted has the story right.


..... Phil


d

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Yet another thump problem. ;-)
 

On Thu, 2 Jun 2016 05:34:23 -0700 (PDT), Phil Allison
wrote:

Don Pearce wrote:

Phil Allison

Don Pearce wrote:



** The non sealed types I have come across develop bad contacts
( high resistance) and cleaning them is PITA.



Mosfets are an excellent alternative to relays these days. On
resistance of a few milliohms in cheap packages.


** Shame about the many drawbacks, like having an *internal diode*
in parallel and needing to be driven with a gate voltage to get that
low resistance.

Not a practical alternative to a DPDT mini-relay you can by for a
couple of dollars.

http://sound.westhost.com/articles/muting.html#s4




Just use enhancement mode devices. Gate up at source voltage - the FET
is off. Drag it down by five volts, it is fully on. Pretty much the
same driving method as a five volt relay. And no contacts to get
dirty.


** Same bull**** as before, one mosfet will not do the job for line level signals and having to bias it on makes it almost useless.

The link I quoted has the story right.


.... Phil

If you say so. It has always worked for me. How do you operate a relay
without having to "bias" it on?

d

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In article ,
Trevor Wilson wrote:
We had an inline monitoring 48/4/2 Neve at Thames with thousands of the
bloody things always giving problems. ;-)


**I'll bet they weren't decent, hermetically sealed, gold contact types,
nor were they used to short the signal to earth. If such relays are used
in that type of application, they almost never exhibit problems.
Whenever I see a product with those clear topped, non-sealed DIL relays,
I know exactly what needs to be done. When the relay is replaced with a
proper one, I never see the job back. There are relays and there are
decent quality relays.

I can't remember the exact spec of them - and they certainly did much more
than simply short to ground. They configured the console for track laying,
overdub or mixdown.

--
*What boots up must come down *

Dave Plowman London SW
To e-mail, change noise into sound.

Yet another thump problem. ;-)
 

On Thu, 02 Jun 2016 13:07:42 +0100, Jim Lesurf
wrote:

In article , Don Pearce
wrote:

Mosfets are an excellent alternative to relays these days. On resistance
of a few milliohms in cheap packages.

And should work OK with something like a 405 that has current limiters.

However I must confess that the impression I've gained is that here the
problem may be being injected into the input of the 405. If so, using small
signal devices to clamp that to ground might be cheaper and more effective.


The Mosfet is ideal for that too. I modelled that on LTSpice, and it
looks perfect. Smaller devices with about 60mOhm channel resistance
are ideal - they have very low gate/channel capacitance and very
little of the operating pulse gets through. My model used a 1k
resistance in series with the signal followed by the Mosfet to ground.

d

---
This email has been checked for viruses by Avast antivirus software.
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Yet another thump problem. ;-)
 

Jim Lesurf wrote:



Mosfets are an excellent alternative to relays these days. On resistance
of a few milliohms in cheap packages.

And should work OK with something like a 405 that has current limiters.


** LOL - no-one here is suggesting shorting the *output* of an amp !!!



However I must confess that the impression I've gained is that here the
problem may be being injected into the input of the 405.


** Duh - you don't say.


If so, using small
signal devices to clamp that to ground might be cheaper and more effective.


** It is actually neither, for many obvious reasons.

Read this link and learn.

http://sound.westhost.com/articles/muting.html#s4



.... Phil

Yet another thump problem. ;-)
 

Don Pearce wrote:



The Mosfet is ideal for that too. I modelled that on LTSpice, and it
looks perfect. Smaller devices with about 60mOhm channel resistance
are ideal - they have very low gate/channel capacitance and very
little of the operating pulse gets through. My model used a 1k
resistance in series with the signal followed by the Mosfet to ground.


** Cleary you have NOT modelled a scheme that mutes switch-on noises OR noises that occur after switch off.

NOR have you worked out how to avoid clipping the audio signal at 0.6V negative.

Read the link I posted and shut up.


..... Phil

Yet another thump problem. ;-)
 

On 2016-06-03 04:40:09 +0000, Phil Allison said:

Don Pearce wrote:



The Mosfet is ideal for that too. I modelled that on LTSpice, and it
looks perfect. Smaller devices with about 60mOhm channel resistance
are ideal - they have very low gate/channel capacitance and very
little of the operating pulse gets through. My model used a 1k
resistance in series with the signal followed by the Mosfet to ground.


** Cleary you have NOT modelled a scheme that mutes switch-on noises OR
noises that occur after switch off.

NOR have you worked out how to avoid clipping the audio signal at 0.6V
negative.

Read the link I posted and shut up.


.... Phil



There are mosfets without the Drain-Source protection diode.

Arthur

--
real email arthur at bellacat dot com